Coated tool

ABSTRACT

A coated tool is, for example, a cutting tool which is provided with a base material and a coating layer located on the base material, wherein a cutting edge and a flank surface are located on the coating layer, the coating layer has a portion in which at least a titanium carbonitride layer and an aluminum oxide layer having an a-type crystal structure are laminated in this order, and, with regard to a texture coefficient (Tc) (hkl) which is calculated on a basis of a peak of the aluminum oxide layer analyzed by an X-ray diffraction analysis, a texture coefficient (Tc1) (146) as measured from a surface side of the aluminum oxide layer in the flank surface is 1 or more.

RELATED APPLICATIONS

The present application is a national stage entry according to 35 U.S.C.§371 of PCT application No.: PCT/JP2015/073639 filed on Aug. 22, 2015,which claims priority from Japanese application No.: 2014-174098 filedon Aug. 28, 2014, and is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to a coated tool comprising a basematerial and a coating layer located on a surface of the base material.

BACKGROUND ART

Conventionally, coated tools are known, such as a cutting tool in whichone or multiple coating layers such as titanium carbide layers, titaniumnitride layers, titanium carbonitride layers, aluminum oxide layers, andtitanium nitride aluminum layers are formed on the surface of a basematerial such as a cemented carbide, a cermet, a ceramic material or thelike.

The occasions where the cutting tool is used for heavy-load intermittentcutting in which a large impact is applied to a cutting edge or the likeare increased with the recent increase in the efficiency of cuttingprocessing. Under such severe cutting conditions, a large impact isapplied to the coating layer, and chipping or the detachment of acoating layer tends to occur. Thus, the improvement in fractureresistance of the coating layer has been demanded for preventing theoccurrence of chipping or the detachment of the coating layer.

As a technique for improving fracture resistance in a cutting tool asmentioned above, Patent Document 1 discloses a technique whereby itbecomes possible to optimize the grain diameters and the layer thicknessof an aluminum oxide layer and to adjust the texture coefficient on face(012) to 1.3 or more to form an aluminum oxide layer that is dense andhas high fracture resistance. Patent Document 2 discloses a techniquewhereby it becomes possible to adjust the texture coefficient on face(012) in an aluminum oxide layer to 2.5 or more to make the residualstress in the aluminum oxide layer to be released easily, therebyimproving the fracture resistance of the aluminum oxide layer.

As a technique for improving wear resistance of a cutting tool asmentioned above, Patent Document 3 discloses a technique whereby itbecomes possible to improve strength and toughness of a coating film byforming an aluminum oxide layer located immediately above anintermediate layer by laminating at least two unit layers havingdifferent X-ray diffraction patterns from each other to form thealuminum oxide layer.

Patent Document 4 discloses a cutting tool in which the texturecoefficient on face (006) in an aluminum oxide layer is increased to 1.8or more and the peak intensity ratio I(104)/I(110) between the peakintensity on face (104) and the peak intensity on face (110) is adjustedto a value falling within a specific range.

Patent Document 5 discloses a cutting tool in which the peak intensityratio I(104)/I(012) between the peak intensity on face (104) to the peakintensity on face (012) in an aluminum oxide layer is adjusted in such amanner that the peak intensity ratio in a first surface of the aluminumoxide layer is larger than that in a second surface of the aluminumoxide layer.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent No. 6-316758

Patent Document 2: Japanese Unexamined Patent Publication No.2003-025114

Patent Document 3: Japanese Unexamined Patent Publication No. 10-204639

Patent Document 4: Japanese Unexamined Patent Publication No.2013-132717

Patent Document 5: Japanese Unexamined Patent Publication No.2009-202264

SUMMARY OF THE INVENTION Means for Solving the Problems

The coated tool according to the present embodiment has a base materialand a coating layer located on a surface of the base material,

wherein a cutting edge and a flank surface are located on the coatinglayer,

the coating layer has a portion in which at least a titaniumcarbonitride layer and an aluminum oxide layer having an α-type crystalstructure are laminated in this order, and

a texture coefficient Tc1 (146) detected in measurement from a surfaceside of the aluminum oxide layer in the flank surface is 1.0 or more,wherein the texture coefficient Tc (hkl) is a value expressed by theformula shown below on the basis of a peak of the aluminum oxide layeranalyzed by an X-ray diffraction analysis:

a texture coefficient Tc (hk1)={I(hkl)/I₀(hkl)}/[(⅛) ×Σ{I(HKL)/I₀(HKL)}]

wherein (HKL) represents a crystal face (012), (104), (110), (113),(024), (116), (214) or (146);

each of I (HKL) and I (hkl) represents a peak intensity of a peak whichis attributed to each crystal face and is detected by an X-raydiffraction analysis of the aluminum oxide layer; and

each of I₀(HKL) and I₀(hkl) represents a reference diffraction intensityof each crystal face contained in a JCPDS card No. 00-010-0173.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic perspective view of a cutting tool that is anexample of the coated tool according to this embodiment.

FIG. 2 shows a schematic cross-sectional view of the cutting toolillustrated in FIG. 1.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

As illustrated in FIG. 1, a cutting tool (simply abbreviated as “atool”, hereinbelow) 1 which is an aspect of the coated tool according tothe present embodiment has such a configuration that one main surfaceand the side surface of the tool 1 serve as a rake surface 2 and a flanksurface 3, respectively, and the intersecting ridgeline portion betweenthe rake surface 2 and the flank surface 3 serves as a cutting edge 4.

As illustrated in FIG. 2, the tool 1 comprises a base material 5 and acoating layer 6 located on a surface of the base material 5. The coatinglayer 6 is a laminate composed of an underlayer 7, a titaniumcarbonitride layer 8, an intermediate layer 9, an aluminum oxide layer10 and a surface layer 11 in this order as observed from a side of thebase material 5. The aluminum oxide layer 10 has an a-type crystalstructure.

In this aspect, a value which is expressed by the formula shown below ina peak of the aluminum oxide layer 10 as determined by an X-raydiffraction analysis is defined as a texture coefficient Tc (hkl).

A texture coefficient Tc (hkl)={I(hkl)/I₀(hkl)}/[(⅛)×Σ{I(HKL)/I₀(HKL)}]

wherein (HKL) represents a crystal face (012), (104), (110), (113),(024), (116), (214) or (146);

each of I (HKL) and I (hkl) represents a peak intensity of a peakattributed to each crystal face which is detected in the X-raydiffraction analysis of the aluminum oxide layer 10;

each of I_(o)(HKL) and I_(o)(hkl) represents a reference diffractionintensity of each crystal face which is contained in a JCPDS card No.00-010-0173; and

Tc1 is defined as a texture coefficient of a surface side peak asmeasured from the surface side of the aluminum oxide layer 10 in theflank surface 3, Tc2 is defined as a texture coefficient of a basematerial side peak which is detected in the measurement in which aportion of the aluminum oxide layer 10 is polished to allow only thebase material side portion of the aluminum oxide layer 10 to leave inthe flank surface 3, and Tc3 is defined as a texture coefficient of thesurface side peak as measured from the surface side of the aluminumoxide layer 10 in the rake surface 2.

According to this embodiment, the texture coefficient Tc1 (146) is 1.0or more. In this case, the wear resistance of the aluminum oxide layer10 is improved. As the result, a tool 1 which can be used for aprolonged period can be produced. It is considered that, when thetexture coefficient Tc (146) is increased, in other words, the ratio ofthe peak intensity I (146) of face (146) is increased, aluminum oxidecrystals that constitute the aluminum oxide layer 10 are likely to bowagainst the impact applied to the aluminum oxide layer 10 in the filmformation direction (i.e., a direction perpendicular to the surface)from the surface side and therefore the resistance to fracture can beimproved. Therefore, it is considered that, on the surface side of thealuminum oxide layer 10, it becomes possible to prevent the occurrenceof fine chipping on the surface of the aluminum oxide layer 10 toprevent the progression of wearing caused by the fine chipping byincreasing the texture coefficient Tc (146). The preferred range of theTc1 (146) is 1.1 to 5.0, particularly preferably 1.5 to 3.5, and morepreferably 1.8 to 3.0.

According to this aspect, when Tc1 (146) is compared with Tc2 (146), Tc1(146) is larger than Tc2 (146). In other words, Tc2 (146) is smallerthan Tc1 (146). When the texture coefficient Tc1 (146) is increased, thecoefficient of thermal expansion in a direction parallel to the surfaceof the aluminum oxide layer 10 is increased, and thus the differencebetween this coefficient of thermalexpansion and the coefficient ofthermalexpansion in the intermediate layer 9 and the titaniumcarbonitride layer 8 which are layers located closer to the basematerial than the aluminum oxide layer 10 does and located below thealuminum oxide layer 10 is increased and therefore the aluminum oxidelayer 10 is likely to detach.

Then, the detachment of the aluminum oxide layer 10 can be prevented byreducing the Tc2 (146) to a value smaller than the Tc1 (146). Thepreferable range of Tc2 (146) is 0.3 to 1.5.

The method for measuring Tc1 (146) and Tc2 (146) of the aluminum oxidelayer 10 is described hereinbelow. The X-ray diffraction analysis on thealuminum oxide layer 10 is carried out with a conventional X-raydiffraction analysis device using a CuKα line. For determining the peakintensity of each crystal face of the aluminum oxide layer 10 from anX-ray diffraction chart, the diffraction angle of each crystal facewhich is contained in a JCPDS card No. 00-010-0173 is checked, thecrystal face of the detected peak is identified, and then the peakintensity of the peak is measured.

In this regard, the identification of a peak detected by the X-raydiffraction analysis is carried out using a JCPDS card. In this case,however, the position of the peak is sometimes displaced by the actionof a residual stress remaining in the coating layer 6 or the like.Therefore, for confirming whether or not the detected peak is a peak ofthe aluminum oxide layer 10, the X-ray diffraction analysis is carriedout in such a state that the aluminum oxide layer 10 is polished, andpeaks detected before and after the polishing are compared with eachother. From this difference, it becomes possible to confirm that thepeak is a peak of the aluminum oxide layer 10.

For the measurement of Tc1 (hkl), a surface side peak which is measuredfrom the surface side of the aluminum oxide layer 10 in the flanksurface 3 is measured. Specifically, a peak intensity of the aluminumoxide layer 10, including the surface side of the aluminum oxide layer10 to the side of the base material 5 of the aluminum oxide layer 10, ismeasured. More specifically, the X-ray diffraction analysis on thecoating layer 6 is carried out in such a state that the surface layer 11is removed by polishing or in such a state that the surface layer 11 isnot polished. The peak intensity of each of the obtained peaks ismeasured, and the texture coefficient Tc1 (hkl) is calculated. In theremoval of the surface layer 11 by polishing, only a portion having athickness of 20% or less of the thickness of the aluminum oxide layer 10may be removed. Alternatively, the X-ray diffraction analysis may becarried out without polishing the surface layer 11, as long as eightpeaks of aluminum oxide can be measured. The surface side peak isdetected including the oriented state on the side of the base material 5of the aluminum oxide layer 10. Because the state of the structure ofthe aluminum oxide layer at a position located close to a surface of thealuminum oxide layer to be measured by the X-ray diffraction analysismore greatly affects a peak, the influence of the oriented state on theside of the base material 5 on the surface side peak is small. Tc3 (hkl)is measured in the same manner on the basis of the surface side peak ofthe aluminum oxide layer 10 in the rake surface 2.

For the measurement of Tc2 (hkl), the peak intensity is measured in sucha state that a portion of the aluminum oxide layer 10 in the flanksurface 3 is polished to allow only the base material portion of thealuminum oxide layer 10 to leave. Specifically, at first, the aluminumoxide layer 10 in the coating layer 6 is polished until the thickness ofthe aluminum oxide layer 10 becomes 10 to 40% of the thickness of theunpolished aluminum oxide layer 10. The polishing is carried out by abrush processing with diamond abrasive grains, a processing with anelastic grind stone, a blast processing or the like. Subsequently, apolished portion of the aluminum oxide layer 10 is subjected to an X-raydiffraction analysis under the same conditions as those employed for themeasurement on the surface side portion of the aluminum oxide layer 10to measure a peak of the aluminum oxide layer 10, and then the texturecoefficient Tc2 (hkl) is calculated.

The texture coefficient Tc can be determined as a ratio relative to thenon-oriented standard data as defined in a JCPDS card, and is thereforea measure that indicates the degree of orientation of each crystal face.The term. “(hkl)” in Tc (hkl) refers to a crystal face of which thetexture coefficient is to be calculated.

According to this aspect, in the surface side peaks measured from thesurface side of the aluminum oxide layer 10 in the flank surface 3, I(116) and I (104) are first most-intense and second most-intense,respectively. In this case, the occurrence of flank wearing caused byfine chipping in the flank surface 3 is likely to be prevented. I (146)has a peak intensity in the top 8 in the peak intensities, particularlydesirably third most-intense to sixth most-intense in the peakintensities.

According to this aspect, the texture coefficient Tc3 (104) is smallerthan Tc1 (104). In this case, the occurrence of crater wear on the rakesurface 2 can be prevented and the chipping resistance on the flanksurface 3 can also be reduced.

As the result of a test, it is found that the chipping resistance of thealuminum oxide layer 10 cannot be improved sufficiently merely byadjusting Tc1 (104) to a value larger than Tc3 (104) and the crater wearresistance of the aluminum oxide layer 10 can be improved greatly whenthe Tc1 (146) is 1.0 or more.

The titanium carbonitride layer 8 is composed of a laminate of aso-called MT (moderate temperature)-titanium carbonitride layer 8 a andan HT-titanium carbonitride layer 8 b which are laminated in this orderfrom the side of the base material. The MT-titanium carbonitride layer 8a is composed of columnar crystals which contain an acetonitrile (CH₃CN)gas as a raw material and is made into a film at a relatively low filmformation temperature of 780 to 900° C. The HT (hightemperature)-titanium carbonitride layer 8 b is composed of granularcrystals which are formed into a film at a high film formationtemperature of 950 to 1100° C. According to this aspect, triangle-shapedprotrusions which are tapered toward the aluminum oxide layer 10 asobserved cross-sectionally are formed on the surface of the HT-titaniumcarbonitride layer 8 b, and the formation of the protrusions enables theincrease in adhesion force of the aluminum oxide layer 10 and theprevention of the detachment of the coating layer 6 or chipping.

According to this aspect, an intermediate layer 9 is located on thesurface of the HT-titanium carbonitride layer 8 b. The intermediatelayer 9 contains titanium and oxygen, and is composed of, for example,TiCO, TiNO, TiCNO, TiAlCO, TiAlCNO or the like. In FIG. 2, theintermediate layer 9 is composed of a laminate of a lower intermediatelayer 9 a and an upper intermediate layer 9 b. In this case, each ofaluminum oxide particles that constitute the aluminum oxide layer 10 hasan a-type crystal structure. The aluminum oxide layer 10 having ana-type crystal structure is highly hard and can increase the wearresistance of the coating layer 6. When the intermediate layer 9 has alaminated structure composed of a lower intermediate layer 9 a made fromTiAlCNO and an upper intermediate layer 9 b made from. TiCNO, an effectof increasing the fracture resistance of the cutting tool 1 can beachieved. Further, when the intermediate layer 9 is composed of TiCO orTiAlCO, Tc1 (146) and Tc2 (146) can be increased. The titaniumcarbonitride layer 8 is provided at a thickness of 6.0 to 13.0 pm, andthe intermediate layer 9 is provided at a thickness of 0.05 to 0.5 μm.

Each of the underlayer 7 and the surface layer 11 is made from titaniumnitride. In other aspects, the underlayer 7 and the surface layer 11 maybe made from other materials such as titanium carbonitride, titaniumcarboxynitride, and chromium nitride other than titanium nitride, and atleast one of the underlayer 7 and the surface layer 11 may beeliminated. The underlayer 7 is provided at a thickness of 0.1 to 1.0μm, and the surface layer 11 is provided at a thickness of 0.1 to 3.0μm.

The thickness of each layer and the properties of crystals constitutingeach layer can be determined by observing an electron microscope image(a scanning electron microscope (SEM) image or a transmission electronmicroscope (TEM) image) of a cross section of the tool 1. In thisembodiment, the wording “the crystal morphology of crystals constitutingeach layer in the coating layer 6 is columnar” means that the ratio ofthe above-mentioned average crystal width to the length of each of thecrystals in the direction of the thickness of the coating layer 6 is 0.3or less on average. On the other hand, when the ratio of the averagecrystal width to the length of each of the crystals in the direction ofthe thickness of the coating layer is more than 0.3 on average, it isdefined that the morphology of the crystals is granular.

On the other hand, the base material 5 in the tool 1 can comprise acemented carbide or Ti-based cermet which is produced by binding a hardphase comprising tungsten carbide (WC) and optionally at least onecomponent selected from the group consisting of a carbide, a nitride anda carbonitride of a metal belonging to Groups 4, 5 or 6 on the periodictable to a binding phase comprising an iron-group metal such as cobalt(Co) and nickel (Ni), or a ceramic material such as Si₃N₄, Al₂O₃,diamond and cubic boron nitride (cBN) . Among these materials, when usedas a cutting tool like the tool 1, the base material 5 preferablycomprises a cemented carbide or a cermet, from the viewpoint of fractureresistance and wear resistance. Depending on the intended use, the basematerial 5 may comprise a metal such as a carbon steel, a high speedsteel and an alloy steel.

Furthermore, the cutting tool is so configured that the cutting edge 4formed at an intersection part between the rake surface 2 and the flanksurface 3 is put to an object to be cut to cut/process the object, andcan exert the above-mentioned excellent effects. The cutting toolaccording to this embodiment can be used as a cutting tool, and also canbe used in various use applications including a digging tool and aknife. In this case, excellent mechanical reliability can be achieved.

Next, the method for producing the coated tool according to the presentembodiment will be described with reference to an example of the methodfor producing the tool 1.

The base material 5 made from a hard alloy is produced by appropriatelyadding a metal powder, a carbon powder or the like to a powder of aninorganic material such as a metal carbide, a nitride, a carbonitrideand an oxide, which can be formed into the hard alloy that can serve asthe base material 5 by sintering, then agitating the mixture, thenmolding the agitated mixture into a predetermined tool shape by a knownmolding method such as press molding, cast molding, extrusion moldingand cold isostatic press molding, and then sintering the molded productunder vacuum or in a non-oxidative atmosphere. If desired, the surfaceof the base material 5 is subjected to a polishing processing or acutting edge honing processing.

Subsequently, a coating layer is formed on the surface of the basematerial 5 by a chemical vapor deposition (CVD) method.

At first, a mixed gas composed of 0.5 to 10 volume % of a titaniumtetrachloride (TiCl₄) gas, 10 to 60 volume % of a nitrogen (N₂) gas anda remainder made up by a hydrogen (H₂) gas is prepared as a reaction gascomposition and then introduced into a chamber, and a TiN layer thatserves as an underlayer 7 is formed at a film formation temperature of800 to 940° C. and at 8 to 50 kPa.

Subsequently, a mixed gas composed of, in volume %, 0.5 to 10 volume %of a titanium tetrachloride (TiCl₄) gas, 5 to 60 volume % of a nitrogen(N₂) gas, 0.1 to 3.0 volume % of an acetonitrile (CH₃CN) gas and aremainder made up by a hydrogen (H₂) gas is prepared as reaction gascomposition and then introduced into a chamber, and a MT-titaniumcarbonitride layer is formed at a film formation temperature of 780 to880° C. and at 5 to 25 kPa. In this case, the content ratio of theacetonitrile (CH₃CN) gas in the later stage of the film formation isincreased compared with that in the initial stage of the film formation,whereby the average crystal width of the titanium carbonitride columnarcrystals that constitute the titanium carbonitride layer in the surfaceside can be increased compared with that in the side of the basematerial.

Subsequently, a HT-titanium carbonitride layer, which constitutes theupper side portion of the titanium carbonitride layer 8, is formed.According to this aspect, specific film formation conditions for theHT-titanium carbonitride layer are as follows: a mixed gas composed of 1to 4 volume % of a titanium tetrachloride (TiC1 ₄) gas, 5 to 20 volume %of a nitrogen (N₂) gas, 0.1 to 10 volume % of a methane (CH₄) gas and aremainder made up by a hydrogen (H₂) gas is prepared and then introducedinto a chamber, and the layer is formed at a film formation temperatureof 900 to 1050° C. and at 5 to 40 kPa.

Subsequently, an intermediate layer 9 is produced. Specific filmformation conditions in this aspect are as follows: at a first stage, amixed gas composed of 3 to 30 volume % of a titanium tetrachloride (TiC1₄) gas, 3 to 15 volume % of a methane (CH₄) gas, 5 to 10 volume % of anitrogen (N₂) gas, 0.5 to 1 volume % of a carbon monooxide (CO) gas, 0.5to 3 volume % of an aluminum trichloride (AlCl₃) gas and a remaindermade up by a hydrogen (H₂) gas is prepared. After the preparation, themixed gas is introduced into a chamber, and a film is formed at a filmformation temperature of 900 to 1050° C. and at 5 to 40 kPa. Accordingto this process, an intermediate layer 9 having an uneven surface can beformed on the surface of the titanium carbonitride layer 8.

Subsequently, as a second stage of the production of the intermediatelayer 9, a mixed gas composed of 3 to 15 volume % of a titaniumtetrachloride (TiCl₄) gas, 3 to 10 volume % of a methane (CH₄) gas, 10to 25 volume % of a nitrogen (N₂) gas, 0.5 to 2.0 volume % of a carbonmonooxide (CO) gas and a remainder made up by a hydrogen (H₂) gas isprepared. After the preparation, the mixed gas is introduced into achamber, and a film is formed at a film formation temperature of 900 to1050° C. and at 5 to 40 kPa. In this process, the nitrogen (N₂) gas maybe replaced by an argon (Ar) gas. According to this process, theunevenness of the surface of the intermediate layer 9 can become fine tocontrol the state of the growth of aluminum oxide crystals in analuminum oxide layer 10 that is to be formed in the subsequent step.

Subsequently, an aluminum oxide layer 10 is formed. At first, cores foraluminum oxide crystals are formed. The formation is carried out using amixed gas composed of 5 to 10 volume % of an aluminum trichloride(AlCl₃) gas, 0.1 to 1.0 volume % of a hydrogen chloride (HCl) gas, 0.1to 5.0 volume % of a carbon dioxide (CO₂) gas and a remainder made up bya hydrogen (H₂) gas at 950 to 1100° C. and at 5 to 10 kPa. Through thisfirst film formation stage, the state of the growth of aluminum oxidecrystals to be formed into a film can be altered to control the Tc2(146) of the aluminum oxide layer 10.

Subsequently, a film is formed using a mixed gas composed of 0.5 to 5.0volume % of an aluminum trichloride (AlCl₃) gas, 1.5 to 5.0 volume % ofa hydrogen chloride (HCl) gas, 0.5 to 5.0 volume % of a carbon dioxide(CO₂) gas, 0 to 1.0 volume % of a hydrogen sulfide (H₂S) gas and aremainder made up by a hydrogen (H₂) gas at 950 to 1100° C. and at 5 to20 kPa. Through this second film formation stage, the state of growth ofaluminum oxide crystals that are to be formed into a film on the side ofthe intermediate layer of the aluminum oxide layer 10 can be controlledto control the Tc2 (146) .

Subsequently, an aluminum oxide layer 10 is formed using a mixed gascomposed of 5 to 15 volume % of an aluminum trichloride (AlCl₃) gas, 0.5to 2.5 volume % of a hydrogen chloride (HCl) gas, 0.5 to 5.0 volume % ofa carbon dioxide (CO₂) gas, 0.1 to 1.0 volume % of a hydrogen sulfide(H₂S) gas and a remainder made up by a hydrogen (H₂) gas at 950 to 1100°C. and at 5 to 20 kPa. Through this third film formation stage, thestate of growth of the aluminum oxide crystals that are to be formedinto a film on the surface side of the aluminum oxide layer 10 can becontrolled to control the Tc1 (146) . The second and third stages in thefilm formation step of the aluminum oxide layer 10 are not independentsteps, and the composition of the mixed gas may change continuously.

If desired, a surface layer (a TiN layer) 11 is formed. Specific filmformation conditions are as follows: a mixed gas composed of 0.1 to 10volume % of a titanium tetrachloride (TiCl₄) gas, 10 to 60 volume % of anitrogen (N₂) gas and a remainder made up by a hydrogen (H₂) gas isprepared as a reaction gas composition and then introduced into achamber, and a film is formed at a film formation temperature of 960 to1100° C. and at 10 to 85 kPa.

Subsequently, if desired, at least a cutting edge part on the surface ofthe formed coating layer 6 is processed by polishing. Through thisprocessing by polishing, the cutting edge part can be made smooth, thewelding of the workpiece material can be prevented, and a tool havingsuperior fracture resistance can be produced. The Tc3 (104) can beadjusted by, for example, polishing only the rake surface.

EXAMPLES

At first, 6% by mass of a metal cobalt powder having a mean particlediameter of 1.2 μm, 0.5% by mass of a titanium carbide powder having amean particle diameter of 2.0 μm, 5% by mass of a niobium carbide powderhaving a mean particle diameter of 2.0 μm and, as a remainder, atungsten carbide powder having a mean particle diameter 1.5 μm wereadded in this content ratio and then mixed together, and the resultantmixture was molded into a tool shape (CNMG120408) by press molding.Subsequently, the molded product was subjected to a binder removaltreatment and then sintered at 1500° C. under vacuum of 0.01 Pa for 1hour to produce a base material composed of a cemented carbide.Subsequently, the resultant base material was subjected to a brushprocessing, and a portion that served as a cutting edge was R-honed.

Subsequently, a coating layer was formed on the base material composedof the cemented carbide by a chemical vapor deposition (CVD) methodunder the film formation conditions shown in Table 1 and subjecting therake surface to a polishing processing as for sample Nos. 1 to 10 toproduce a cutting tool. In Tables 1 and 2, the name of each compound wasexpressed in its chemical symbol.

In the above-mentioned sample, an X-ray diffraction analysis with CuKαline was carried out on the rake surface without polishing the coatinglayer, and a texture coefficient Tc3 (hkl) of each of crystal faces(146), (104) and (116) in a JCPDS card was calculated. Subsequently, anX-ray diffraction analysis with CuKα line was carried out on theflattened surface of the flank surface without polishing the coatinglayer, and a surface side peak (in the tables, referred to as “surfaceside” or “surface side peak”) measured from the surface side of thealuminum oxide layer was identified and a peak intensity of each peakwas measured. The first most-intense peak and the second most-intensepeak in the surface side peaks were confirmed, and a texture coefficientTc1 (hkl) of each of the crystal faces (146), (104) and (116) in theJCPDS card was calculated. The flank surface was polished until thethickness became 10 to 40% of the thickness of the aluminum oxide layer,and then subjected to an X-ray diffraction analysis in the same manneras mentioned above to identify a base material side peak (in the tables,referred to as “base material side”) measured in such a state that aportion of the aluminum oxide layer was polished to allow only the basematerial side to leave and the peak intensity of each peak was measured.By employing the peak intensity of each peak, a texture coefficient Tc2(hkl) of each of crystal faces (146), (104) and (116) was calculated. Inthe above-mentioned X-ray diffraction measurements, the measurement wascarried out on arbitrary three samples and an average of the results onthe three samples was employed for the evaluation. In addition, thefracture surface of the tool was observed on a scanning electronmicroscope (SEM) to measure the thickness of each layer. The results areshown in Tables 2 to 4.

Subsequently, a continuous cutting test and an intermittent cutting testwere carried out using the resultant cutting tool under thebelow-mentioned conditions to evaluate wear resistance and fractureresistance. The results are shown in Table 4.

(Continuous cutting conditions)

Workpiece material: a chromium molybdenum steel material (SCM435)

Tool shape: CNMG120408

Cutting speed: 300 m/min

Feed speed: 0.3 mm/rev

Depth of cut: 1.5 mm

Cutting time: 25 min

Other: a water-soluble cutting solution was used

Items of evaluation: a honed cutting edge was observed on a scanningelectron microscope, and a flank wear width in a flank surface and acrater wear width in a rake surface in an actually worn portion weremeasured.

(Intermittent Cutting Conditions)

Workpiece material: a chromium molybdenum steel, a four-grooved steelmaterial (SCM440)

Tool shape: CNMG120408

Cutting speed: 300 m/min

Feed speed: 0.3 mm/rev

Depth of cut: 1.5 mm

Other: a water-soluble cutting solution was used

Item of evaluation: the number of impacts that might trigger defects wasmeasured.

TABLE 1 Chamber Coating temperature Pressure layer Mixed gas composition(% by volume) (° C.) (kPa) TiN-1 TiCl₄: 2.5, N₂: 23, H₂: balance 900 16TiCN-1(MT) TiCl₄: 1.0, N₂: 10, CH₃CN: 0.1→0.4, H₂: balance 850 9TiCN-2(HT) TiCl₄: 1.0, N₂: 10, CH₄: 2.0, H₂: balance 1010 9 TiAlCNO-1TiCl₄: 7.0, CH₄: 5.5, N₂: 5.0, CO: 0.5, AlCl₃: 1.5, H₂: balance 1000 15TiCNO-1 TiCl₄: 7.0, CH₄: 3.5, N₂: 15.0, CO: 1.0, H₂: balance 1000 15Al₂O₃-1 AlCl₃: 8.0, HCl: 0.5, CO₂: 1.0, H₂: balance 1000 10 Al₂O₃-2AlCl₃: 3.5, HCl: 2.0, CO₂: 1.0, H₂S: 0.5, H₂: balance 1000 10 Al₂O₃-3AlCl₃: 7.0, HCl: 1.0, CO₂: 1.0, H₂S: 0.5, H₂: balance 1000 10 Al₂O₃-4AlCl₃: 2.5→5.0, HCl: 2.0→0.5, CO₂: 1.3, H₂S: 0.1, H₂: balance 1000 10Al₂O₃-5 AlCl₃: 6.5, HCl: 1.0, CO₂: 1.5, H₂: balance 1000 10 Al₂O₃-6AlCl₃: 6.0, HCl: 1.0, CO₂: 1.2, H₂S: 0.4, H₂: balance 1000 10 Al₂O₃-7AlCl₃: 4.0, HCl: 2.0, CO₂: 3.0, H₂S: 0.7, H₂: balance 970 20 Al₂O₃-8AlCl₃: 8.0, HCl: 0.5, CO₂: 3.0, H₂S: 0.6, H₂: balance 1050 10 Al₂O₃-9AlCl₃: 5.0→12, HCl: 2.0→1.5, CO₂: 3.0, H₂S: 0.3, H₂: balance 990 10Al₂O₃-10 AlCl₃: 2.0, HCl: 5.0, CO₂: 1.0, H₂: balance 1005 6 TiN-2 TiCl₄:2.0, N₂: 40, H₂: balance 1010 80 *Al₂O₃-3, Al₂O₃-8: The amounts of eachgas (AlCl_(3,)CO_(2,)H₂S) in a mixed gas were changed from x to ycontinuously.

TABLE 2 Coating layer¹⁾ Sample Surface No. Underlayer TiCN layerIntermediate layer Al₂O₃ layer layer 1 — TiCN-1 TiCN-2 TiAlCNO-1 TiCNO-1Al₂O₃-1 Al₂O₃-2 Al₂O₃-3 TiN-2 (9) (0.2) (0.2) (0.1) (<0.1) (2) (5) (1.0)2 TiN-1 TiCN-1 TiCN-2 TiAlCNO-1 TiCNO-1 Al₂O₃-1 Al₂O₃-4 TiN-2 (0.5) (9)(0.5) (0.1) (0.1) (<0.1) (7) (2.0) 3 TiN-1 TiCN-1 TiCN-2 TiAlCNO-1TiCNO-1 Al₂O₃-5 Al₂O₃-2 Al₂O₃-6 TiN-2 (0.5) (12) (0.1) (0.05) (0.05)(<0.1) (3) (4) (1.5) 4 TiN-1 TiCN-1 TiCN-2 TiAlCNO-1 TiCNO-1 Al₂O₃-1Al₂O₃-7 Al₂O₃-8 — (1.0) (8) (0.3) (0.1) (0.1) (<0.1) (1) (6) 5 TiN-1TiCN-1 TiCN-2 — TiCNO-1 Al₂O₃-1 Al₂O₃-9 TiN-2 (0.5) (6) (0.5) (0.5)(<0.1) (7) (3.0) 6 TiN-1 TiCN-1 TiCN-2 TiAlCNO-1 TiCNO-1 Al₂O₃-2 TiN-2(1.0) (6) (0.5) (0.1) (0.1) (7) (1.0) 7 TiN-1 TiCN-1 TiCN-2 TiAlCNO-1TiCNO-1 Al₂O₃-5 Al₂O₃-3 Al₂O₃-2 TiN-2 (0.5) (9) (0.1) (0.1) (0.1) (<0.1)(2) (5) (0.5) 8 TiN-1 TiCN-1 TiCN-2 TiAlCNO-1 TiCNO-1 Al₂O₃-4 TiN-2(0.5) (10) (0.3) (0.1) (0.1) (7) (2.0) 9 TiN-1 TiCN-1 TiCN-2 TiAlCO-1TiCO-1 Al₂O₃-1 Al₂O₃-7 Al₂O₃-8 TiN-2 (1.0) (8) (0.3) (0.1) (0.1) (<0.1)(1) (6) (0.5) 10 TiN-1 TiCN-1 TiCN-2 TiAlCO-1 — Al₂O₃-1 Al₂O₃-7 Al₂O₃-8TiN-2 (1.0) (8) (0.3) (0.1) (<0.1) (1) (6) (1.0) 11 TiN-1 TiCN-1 TiCN-2TiAlCNO-1 TiCNO-1 Al₂O₃-1 Al₂O₃-2 Al₂O₃-3 TiN-2 (1.0) (8) (0.1) (0.2)(0.1) (<0.1) (3) (4) (2.0) *¹⁾Values in parentheses represent the layerthickness in μm.

TABLE 3 Surface side peak First Second Texture coefficient Tc of Al₂O₃layer most- most- Sample Tc1 Tc2 Tc3 Tc1 Tc2 Tc3 Tc1 Tc2 Tc3 intenseintense No. (146) (146) (146) (116) (116) (116) (104) (104) (104) peakpeak 1 1.0 0.5 1.2 0.9 0.4 0.7 2.2 0.7 2.2 (104) (116) 2 2.5 1.1 1.8 1.60.4 1.4 2.6 1.1 2.3 (116) (104) 3 2.0 0.8 1.7 1.1 0.3 1.0 2.1 0.5 2.1(104) (116) 4 2.8 1.2 1.5 2.2 0.7 1.7 3.2 1.8 2.7 (104) (116) 5 1.5 0.71.0 0.8 0.5 0.7 1.8 1.5 1.8 (110) (104) 6 0.9 0.6 0.8 1.3 0.4 1.2 2.01.2 2.1 (104) (012) 7 0.7 0.9 0.5 0.6 0.7 0.5 2.0 1.7 2.0 (012) (110) 80.8 0.8 0.9 1.0 0.4 0.9 1.7 0.8 1.8 (104) (110) 9 3.6 1.5 2.0 2.3 0.71.9 3.4 1.9 2.9 (104) (116) 10 3.1 1.3 1.9 2.3 0.7 1.8 3.5 2.0 2.8 (104)(116) 11 1.0 0.5 1.0 0.9 0.4 0.9 2.2 0.7 2.2 (104) (116)

TABLE 4 Cutting performance Sample Crater wear width Flank wear widthNo. Kb (mm) Vb (mm) Number of impacts 1 0.22 0.17 3200 2 0.13 0.13 35503 0.17 0.15 3300 4 0.12 0.10 3700 5 0.28 0.21 3050 6 0.40 0.33 2650 70.46 0.45 2200 8 0.36 0.30 2550 9 0.11 0.09 3800 10 0.11 0.10 3750 110.29 0.18 3100

According to the results shown in Tables 1 to 4, in sample Nos. 6 to 8,in each of which the Tc1 (146) value was less than 1.0, the progressionof wearing was rapid and the aluminum oxide layer was detached easily bythe application of an impact.

On the other hand, in sample Nos. 1 to 5 and 9 to 11, in each of whichthe Tc1 (146) value was 1.0 or more, the fine chipping in the aluminumoxide layer was prevented and the aluminum oxide was rarely detached.Particularly, in sample Nos. 1 to 4 and 9 to 11, in each of which faces(104) and (116) respectively had the first most-intense peak and thesecond most-intense peak among the surface side peaks of the aluminumoxide layer, the flank wear widths were smaller compared with that ofsample No. 5 and the number of impacts was large. Furthermore, in sampleNos. 2, 4, 9 and 10, in each of which the texture coefficient Tc3 (104)of the surface side peak in the rake surface was smaller than thetexture coefficient Tc1 (104) of the surface side peak in the flanksurface, particularly the crater wear width was small.

DESCRIPTION OF THE REFERENCE NUMERALS

1: Cutting tool

2: Rake surface

3: Flank surface

4: Cutting edge

5: Base material

6: Coating layer

7: Underlayer

8: Titanium carbonitride layer

8 a: MT-titanium carbonitride layer

8 b: HT-titanium carbonitride layer

9: Intermediate layer

9 a: Lower intermediate layer

9 b: Upper intermediate layer

10: Aluminum oxide layer

11: Surface layer

1. (canceled)
 2. The coated tool according to claim 5[[1]], wherein atexture coefficient Tc2 (146), which is detected by the measurement inwhich a the first portion is polished to allow only a side of the basematerial of the second layer to leave, is smaller than the Tc1 (146). 3.The coated tool according to claim 5, wherein one of I(116) and I(104)is the first most-intense peak and another one of I(104) and I(116) isthe second most-intense peak among surface side peaks detected inmeasurement from above a top surface of the first portion.
 4. The coatedtool according to claim 5, wherein a texture coefficient Tc3 (104) whichis measured from above a top surface of the second portion is smallerthan a texture coefficient Tc1 (104) which is measured from above thetop surface of the first portion.
 5. A coated tool comprising, a basematerial comprising a first surface and a second surface; and coatinglayers located over the base material and comprising, a first layerincluding titanium carbonitride and located over the base material, anda second layer including aluminum oxide having an alpha-type crystalstructure and located over the first layer; wherein the second layercomprises a first portion located over the first surface and a secondportion located over the second surface, and a texture coefficient Tc1(146) as measured from above a top surface of the first portion is 1 ormore, wherein the texture coefficient Tc (hkl) is a value expressed bythe formula shown below on the basis of a peak of the second layeranalyzed by an X-ray diffraction analysis: a texture coefficient Tc(hkl)={I(hkl)/I₀(hkl)}/[(⅛)×Σ{I(HKL)/I₀(HKL)}] wherein (HKL) representsa crystal face (012), (104), (110), (113), (024), (116), (214) or (146);each of I(HKL) and I(hkl) represents a peak intensity of a peak which isattributed to each crystal face and is detected by an X-ray diffractionanalysis of the second layer; and each of I₀(HKL) and Io(hkl) representsa reference diffraction intensity of each crystal face contained in aJCPDS card No. 00-010-0173.
 6. The coated tool according to claim 5,wherein the top surface of the first portion comprises a flank surface.7. The coated tool according to claim 5, wherein a top surface of thesecond portion comprises a rake surface.